EP0184334A1 - Methods of and apparatus for determining maximum spray flow limits of attemperators - Google Patents

Methods of and apparatus for determining maximum spray flow limits of attemperators Download PDF

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Publication number
EP0184334A1
EP0184334A1 EP85308068A EP85308068A EP0184334A1 EP 0184334 A1 EP0184334 A1 EP 0184334A1 EP 85308068 A EP85308068 A EP 85308068A EP 85308068 A EP85308068 A EP 85308068A EP 0184334 A1 EP0184334 A1 EP 0184334A1
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EP
European Patent Office
Prior art keywords
enthalpy
steam
block
attemperator
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP85308068A
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German (de)
English (en)
French (fr)
Inventor
James L. Barkan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Babcock and Wilcox Co
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Babcock and Wilcox Co
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Filing date
Publication date
Application filed by Babcock and Wilcox Co filed Critical Babcock and Wilcox Co
Publication of EP0184334A1 publication Critical patent/EP0184334A1/en
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22G—SUPERHEATING OF STEAM
    • F22G5/00—Controlling superheat temperature
    • F22G5/12—Controlling superheat temperature by attemperating the superheated steam, e.g. by injected water sprays

Definitions

  • This invention relates to methods of and apparatus for determining maximum spray flow limits of attemperators.
  • U.S. Patent No. US-A-3 428 557 discloses an apparatus for controlling the amount of chemical additives added to water being supplied to the boiler, and the blowdown rate for the boiler (rate of removing liquid from the boiler) depending on the measured conductivity of a sample of boiler water tapped from the blowdown line of the boiler. This reference is relevant for its showing of an electronic mechanism for controlling at least one parameter of a boiler.
  • a method of determining the maximum spray flow limit of an attemperator having a spray flow thereto the method being characterised by:
  • apparatus for determining the maximum spray flow limit of an attemperator having a spray flow thereto the apparatus being characterised by:
  • a method of determining the maximum spray flow for an attemperator being characterised by measuring the inlet temperature and pressure of the attemperator, using the inlet pressure to determine a base steam inlet enthalpy for steam at a known temperature, using the base enthalpy and a correction factor based on the inlet temperature to establish a corrected base enthalpy, subtracting the corrected base enthalpy from actual steam inlet enthalpy calculated as a function of the inlet pressure to obtain an enthalpy difference, dividing the enthalpy difference by a spray inlet enthalpy difference which is obtained by subtracting the corrected base inlet enthalpy from the spray inlet enthalpy representing enthalpy of spray flow on the attemperator, and multiplying the result of the division by a value corresponding to the main steam flow to obtain the maximum spray flow limit.
  • the spray flow limit is calculated from inlet temperature and pressure readings as well as flow measurements. These measurements are utilised to indicate the steam and water enthalpies (heat contents) entering the attemperator.
  • the limit is based on design information and does not require field information. Determination of maximum spray flow is based on a heat balance calculation around the attemperator. Since the outlet of the attemperator is known from design information, to make the calculation, only measurements to determine inlet conditions are required.
  • the ratio of spray flow to outlet steam flow is the same ratio as inlet steam enthalpy minus limit enthalpy divided by inlet steam enthalpy minus spray medium enthalpy.
  • spray water enthalpy may also be established as a function of load from the plant heat balance information, which information is available from the manufacturer of a turbine to be powered by the boiler. This is acceptable because spray water enthalpy does not have a major effect on the heat balance calculation around the attemperator.
  • the limit enthalpy can be determined from only a pressure reading since the desired temperature can be established in the design stage of the unit.
  • the limit can be taken from a curve relating actual temperature to saturation temperature or, if required, the limit could be lowered to below the saturation curve for the fluid passing through the attemperator.
  • the limit can be reduced because it does not require making the attemperator outlet temperature measurement.
  • a lower limit in the design stage would result in a cost reduction since some units may not require two stages of attemperation if additional spray can be placed through the first attemperator.
  • the determination of steam enthalpy entering the attemperator requires both a temperature and a pressure measurement. By assuming either a constant temperature or enthalpy, a base enthalpy can be established as a function of the other measurement (e.g. pressure). Actual enthalpy is then determined by modifying the base enthalpy for actual temperature and pressure. The accuracy of the enthalpy is a function of the factors used to modify the base enthalpy.
  • the preferred embodiment comprises a combination of interconnected simple function blocks for achieving multiplication, summation, division and subtraction functions.
  • the apparatus illustrated therein is operable to determine a maximum spray flow limit for an attemperator, which limit is outputted on a line 44, on the basis of inlet parameters for the attemperator including attemperator inlet pressure and temperature.
  • the inlet pressure P of the attemperator is taken by a pressure sensor 10 and the inlet temperature T is taken by a temperature sensor 12.
  • An element 14 provides a constant A corresponding to a preselected temperature, in this case 399°C (750°F), which is utilised to obtain a base enthalpy quantity as will be explained later.
  • the value of 399 0 C (750°F) is subtracted from the actual temperature supplied by the temperature sensor 12, in a comparator or subtraction unit 16.
  • K 1 is a function of the attemperator structure and in the present case is 0.0065 when measurements are taken in SI units (1.5 when enthalpy is given in Btu/lb, pressure is given in lbf/in 2 gauge, and temperature is given in °F, hereinbelow referred to as non-metric units).
  • the output of the function block 18 represents a correction for temperature and is multiplied by a first function f(x) 1 which is outputted by a function block 22. As shown in Figure 2, the function block 22 will output a quantity up to 1, depending on the pressure value supplied to the function block 22 by the pressure sensor 10. The multiplication takes place in a block 20 and the output of the block 20 corresponds to a corrected temperature influence on the actual enthalpy.
  • the temperature influence is supplied to a summing block (function block) 28, as is a second function f(x) 2 outputted by a function block 24.
  • the output f(x) 2 of the function block 24 is illustrated in Figure 3 and is related to the attemperator inlet pressure.
  • the second function f(x) 2 corresponds to a base enthalpy for the preselected temperature of 399°C (750°F).
  • a limit enthalpy function f(x) 3 is generated by a third function block 26 from the inlet pressure and is chosen to be that for saturated steam. The difference between the saturated steam enthalpy and the base enthalpy is taken in a second subtracting unit 30.
  • Spray water enthalpy is determined by multiplying a spray water temperature T' from a second temperature sensor 40, in a constant factor function block 38.
  • the spray water temperature is multiplied by a constant K 2 , which is a characteristic of the attemperator.
  • K 2 in the present case is 0.00426 when measurements are taken in SI units (0.91 in non-metric units).
  • the value from the function block 38 is subtracted from the base enthalpy from the summing block 28 is a third subtracting unit 34, and the results from the subtracting units 30 and 34 are divided in a division unit (function block) 32.
  • An alternative way of incorporating the influence of the spray water is by using a fourth function block 42 which provides a fourth function f(x) 4 and can be connected directly to the division unit 32.
  • the curve of Figure 5 shows how the unit load or main steam flow (in percent) is related to the fourth function f(x) 4 and can result in the spray water enthalpy.
  • the result of the division in the division unit 32 is multiplied in a multiplication block 36 by the unit load or main steam flow which is provided on a line 46.
  • Attemperator inlet temperature -399°C (750°F) 28C° (50F°). This calculation is achieved in the function block 16.
  • the maximum spray flow limit thus is equal to 3.82 x 10 4 kg/s (303 Mlb/h). This value is outputted on the line 44.
  • the acceptability of the procedure according to the preferred embodiment can be determined by calculating the actual outlet steam condition and comparing it to the saturation curve which was assumed to be the limit enthalpy.
  • Inlet steam at 427°C (800°F) and 13.8 MPa (2,000 lbf/in 2 ) gauge pressure produces an actual enthalpy of 3.105MJ/kg (1,335 Btu/lb).
  • Spray water at 154°C (310°F) produces an actual enthalpy of 0.660MJ/kg (284 Btu/lb). Attemperator heat balance is thus
  • Outlet steam enthalpy is calculated to 2.642 MJ/kg (1136 Btu/Ib) which agrees quite well with the saturation enthalpy at 13.8 Pa (2,000 lbf/in 2 ) gauge of 2.644 MJ/kg (1137 Btu/lb).

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Measuring Volume Flow (AREA)
  • Electrostatic Spraying Apparatus (AREA)
EP85308068A 1984-11-07 1985-11-06 Methods of and apparatus for determining maximum spray flow limits of attemperators Withdrawn EP0184334A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US66927184A 1984-11-07 1984-11-07
US669271 1984-11-07

Publications (1)

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EP0184334A1 true EP0184334A1 (en) 1986-06-11

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ID=24685765

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Application Number Title Priority Date Filing Date
EP85308068A Withdrawn EP0184334A1 (en) 1984-11-07 1985-11-06 Methods of and apparatus for determining maximum spray flow limits of attemperators

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EP (1) EP0184334A1 (enrdf_load_html_response)
JP (1) JPS61153303A (enrdf_load_html_response)
AU (1) AU4822085A (enrdf_load_html_response)
CA (1) CA1234918A (enrdf_load_html_response)
ES (1) ES8801024A1 (enrdf_load_html_response)
IN (1) IN165703B (enrdf_load_html_response)
ZA (1) ZA857665B (enrdf_load_html_response)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3121442A1 (de) * 1981-05-29 1983-01-05 Steag Ag, 4300 Essen Verfahren zur regelung der temperatur von in einer leitung stroemenden dampf durch einspritzung und anordnung zur durchfuehrung des verfahrens

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5888505A (ja) * 1981-11-20 1983-05-26 株式会社日立製作所 タ−ビンバイパス系の減温制御装置

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3121442A1 (de) * 1981-05-29 1983-01-05 Steag Ag, 4300 Essen Verfahren zur regelung der temperatur von in einer leitung stroemenden dampf durch einspritzung und anordnung zur durchfuehrung des verfahrens

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IEEE TRANSACTIONS ON NUCLEAR SCIENCE, vol. NS-28, no. 1, February 1981, pages 891-896; R.M. CARUSO et al.: "Design and qualification of a microprocessor subcooled margin monitor" *

Also Published As

Publication number Publication date
IN165703B (enrdf_load_html_response) 1989-12-23
ES548465A0 (es) 1987-12-01
CA1234918A (en) 1988-04-05
ZA857665B (en) 1986-05-28
JPS61153303A (ja) 1986-07-12
AU4822085A (en) 1986-05-15
ES8801024A1 (es) 1987-12-01

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